The Complete Guide to Retatrutide in 2026

Retatrutide is a triple hormone receptor agonist. It activates three receptors:

• GLP-1: reduces appetite, slows stomach emptying, and improves blood sugar
• GIP: enhances insulin release and appears to strengthen GLP-1 effects
• Glucagon: thought to increase energy expenditure and fat burning, especially in the liver

By comparison, semaglutide targets one receptor (GLP-1) and tirzepatide targets two (GLP-1 and GIP). Retatrutide's added glucagon activity is what sets it apart.

In 2026, retatrutide reported positive results across five Phase 3 trials.

TRIUMPH-1 (Obesity): In TRIUMPH-1, which enrolled 2,339 adults, the 12 mg dose produced an average of 28.3% weight loss (about 70 lbs) at 80 weeks. Nearly half of participants on 12 mg lost at least 30% of their body weight. Among people with a starting BMI of 35 or higher, average weight loss reached 30.3% at 104 weeks. Even the lowest dose, 4 mg, produced close to 20% weight loss.

TRIUMPH-2 (Obesity + Type 2 Diabetes): Adults with obesity and type 2 diabetes lost up to 20.8% (about 50 lbs) at 80 weeks, along with improvements in A1C.

TRIUMPH-3 (Severe Obesity + Cardiovascular Disease): In adults with a BMI of 35 or higher and established heart disease, retatrutide produced up to 22.6% weight loss and reduced several cardiovascular risk factors. Long-term cardiovascular outcomes are still being studied.

TRIUMPH-4 (Obesity + Knee Osteoarthritis): Participants on 12 mg lost an average of 28.7% of body weight at 68 weeks and reported significant reductions in knee pain.

TRANSCEND-T2D-1 (Type 2 Diabetes): Adults with type 2 diabetes on 12 mg lost an average of 16.8% of body weight at 40 weeks.

Common side effects: Like other GLP-1-based compounds, retatrutide's most common side effects are digestive, especially during dose increases. On the 12 mg dose in TRIUMPH-1:

• Nausea: about 42%
• Diarrhea: about 32%
• Constipation: about 26%
• Vomiting: about 25%

Dysesthesia: Retatrutide causes a side effect rarely seen with other GLP-1s: dysesthesia, an unusual skin sensation such as tingling, burning, or pins and needles. In TRIUMPH-1, it affected about 12% of people on 9 mg and 12 mg, compared with under 1% on placebo. It was usually mild to moderate and often resolved.

Discontinuation rates: Discontinuation due to side effects at the highest doses ranged from about 8% to 18% across trials, compared with about 4–5% on placebo. Lower doses were generally closer to placebo.

Long-term safety: Full Phase 3 data are still being published and peer-reviewed. Retatrutide's long-term safety profile is not yet established.

Is retatrutide FDA-approved? No.

Eli Lilly has said the 2026 trial results provide the data needed to support global submissions, and the company plans to submit a Biologics License Application (BLA) to the FDA in the first quarter of 2027. FDA review typically takes about 10 to 12 months, so approval, if granted, would most likely come in late 2027 or 2028.

These numbers come from separate trials, so comparisons are approximate. In SURMOUNT-5, a head-to-head trial, tirzepatide produced 20.2% weight loss versus 13.7% for semaglutide. Retatrutide hasn't yet been compared head-to-head with either.

If approved, retatrutide could be an option for:

• People with obesity who need significant weight loss
• People who didn't reach their goals on semaglutide or tirzepatide
• People with obesity-related conditions like knee osteoarthritis, sleep apnea, or type 2 diabetes

Final approved uses will depend on the FDA's review.

• What is retatrutide? An investigational once-weekly triple agonist that targets GLP-1, GIP, and glucagon receptors for weight loss and metabolic health.
• How much weight can you lose on retatrutide? In TRIUMPH-1, people on the 12 mg dose lost an average of 28.3% of body weight at 80 weeks.
• When will retatrutide be available? Lilly plans to file with the FDA in early 2027, which points to possible approval in late 2027 or 2028.
• Is retatrutide stronger than tirzepatide? In trials, yes: about 28% average weight loss versus about 21% for tirzepatide's top dose.
• What are the side effects of retatrutide? Mostly nausea, diarrhea, constipation, and vomiting. Some people also experience dysesthesia, a tingling or burning skin sensation.
• Is retatrutide sold online legal? Retatrutide sold online is not a legitimate or regulated product. It's only legally available through clinical trials.

• Retatrutide is a triple agonist targeting GLP-1, GIP, and glucagon.
• Phase 3 trials showed up to 28.3% weight loss at 80 weeks.
• Side effects are mostly GI, plus dysesthesia in some users.
• Retatrutide is not FDA-approved; Lilly plans to file in Q1 2027.
• Products sold online are unregulated and not legitimate.

• Eli Lilly – Retatrutide TRIUMPH-1 Phase 3 Topline Results
• BioSpace – Retatrutide Successful in TRIUMPH-2 and TRIUMPH-3
• Patient Care – Retatrutide Achieved Up to 22.6% Weight Loss in 2 Phase 3 Trials
• Drug Topics – Retatrutide Delivers Weight Loss and A1C Improvements
• The Pharmaceutical Journal – Phase III Retatrutide Study Demonstrates 30% Weight Loss
• Endocrine Society – Retatrutide Phase 3 Safety Data
• TechTarget – TRIUMPH-4 Results
• Weill Cornell Medicine – SURMOUNT-5 Head-to-Head Trial
• Drugs.com – Retatrutide FDA Approval Status